Filamentous fungi are extensively used in fermentation processes in the Biotech industry for production of e.g. enzymes. Growing fungi in a submerged cultivation in reactors often include a substantial mycelia adhesion to the equipment, making the culture heterogeneous. This potentially gives rise to problems as lower productivity and conidia formation as well as a complicated and time consuming cleaning of the equipment. Hydrophobins are proteins forming a hydrophobic coating of both spores and mycelia and these proteins are suspected to be an important cause of the adhesion problem in cultivations with filamentous fungi.
U.S. Pat. No. 7,338,779 relates to submerged fermentation in an aerated and agitated bioreactor and describes methods for reducing foam production in a Tricoderma strain by non-selective deleting of every hydrophobin genes of the genome. The hydrophobin deficient Tricoderma strain displays less attachment of the cultivation medium to the fermentor surfaces, electrodes, impeller, etc, while the amounts of proteins secreted to the culture medium is increased. U.S. Pat. No. 7,338,779 further suggests that the strategy of deleting the hydrophobin genes may also be applied to Aspergillus spp.
A drawback of the above strategy of non-selective deletion of all hydrophobin genes in the cause of reducing the adherence of the fungus to the hardware is that functions of the hydrophobin may have other effects that are detrimental to the fermentation process.